1. Field of the Invention
The present invention relates to an electromagnetic device which has a stator constructed by a plurality of spirally stacked magnetic plates.
2. Description of Related Art
It is conventionally proposed by Japanese Laid-open Patent Publication No. 4-365305, for instance, to construct a solenoid stator for an electromagnetic device by stacking spirally a plurality of magnetic plates having a uniform plate thickness. This electromagnetic device is shown in FIG. 14. In this device, a coil 6 is wound in a coil insertion groove 6 of a stator 4 and a push rod 11 coupled with an armature 12 is disposed slidably movably in a through hole 7 formed at the central part of the stator 4. According to this construction, when the coil 6 is energized, the armature 12 is attracted toward the magnetic pole face (upper or top face in the figure) of the stator 4 so that a valve body (not shown) coupled with the bottom end of the push rod 45 opens and closes.
According to this conventional device, the stator 4 and the armature 12 are likely to attract each other by the magnetic force during the coil energization, causing such drawbacks as when the stator 4 rises and is displaced. That is, in the case of the stator constructed by stacking numerous magnetic plates spirally, the central part of the stator is not supported sufficiently and hence the central part tends to rise causing rising displacement. Such a rising of the stator central part causes the air gap provided between the stator and the armature to decrease, thus affecting the performance of the electromagnetic device or the like.
It is also proposed in Japanese Laid-open Patent Publication No. 3-125086 to regulate the rising of a solenoid stator for an electromagnetic device by a stator support structure for an electromagnetic device. According to this structure, a stator is constructed by stacking E-shaped magnetic plates and pressing the peripheral end face of the stator by a support member. AS shown in FIG. 15 in more detail, the stator 4 has thin magnetic plates 51 stacked at both right and left positions and a thick plate 52 disposed centrally so that the stator 4 is shaped in a generally cylindrical form as a whole. The plate 52 is formed a through hole 7 for insertion of a push rod.
This conventional device has, as shown in FIGS. 16(a) and 16(b), a coil 6, armature 12 and the like with the stator 4. As shown in the figures, an annular support member 54 is mounted on the upper face of the stator 4 thereby to press the longitudinal end (both end parts of all the magnetic plates 51 and 52). Although the stator 4 and the armature 12 operate to attract each other during energization of the coil 6 also in this construction, the stator 4 is regulated from being displaced by the support member 54 which presses the stator 4.